Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$186.85	11.687%	$208.6872	$208.69	$208.70	$208.70
Purchase #2	$148.96	12.365%	$167.3789	$167.38	$167.40	$167.40
Purchase #3	$100.98	10.838%	$111.9242	$111.92	$111.90	$111.90
Purchase #4	$68.83	5.457%	$72.5861	$72.59	$72.60	$72.60
Purchase #5	$223.76	5.408%	$235.8609	$235.86	$235.85	$235.90
Purchase #6	$175.71	13.428%	$199.3043	$199.30	$199.30	$199.30
Purchase #7	$130.30	8.462%	$141.326	$141.33	$141.35	$141.30
7 purchase totals =	$1,035.39		$1,137.0676	$1,137.07	$1,137.10	$1,137.10